Rows: ~49,917,839 Inno DB latin1_swedish_ci Size: 28.7 Gi B I've now yet been able to repeat with 100% accuracy.
The only way to not acquire the query cache mutex in My SQL pre-5.5 is to compile My SQL without query cache. For My SQL 5.5 , to completely disable the query cache (thus, not acquiring the query cache mutex) is required to set query_cache_type=OFF at startup (not at runtime).
That also means that if query_cache_type=OFF at startup, you need to restart My SQL if later you want to enable the query cache (you can’t enable it at runtime).
After fixing some major issues on my slave I started to sync it with the master and observed that it was doing it really slow ....found "invalidating query cache entries (table)" to appear in my process list every now and the....
i checked the Qcache variable but didnt seem to be out of the ordinary, checked my innodb status but no clues there...started searching the web and found the issue could be with the binlog format being row...i tested with the same data set on my test machine and binlog format being statement ....didnt see any such thing there....seached more and found a bug